Full stats in tournament and exhibition modes
At the main menu, hold R and press Left, Up(2), Down, Right, L.

Full stats in movie mode
At the main menu, hold R and press Right, Down(2), Up, Left, L.

Easy knock downs
In movie or any other mode, when the fighter approaches you at the start of the fight, hit him with your special power punch. When he comes to you again, hit him with another special power punch, then attack him with body shots. This will drop his strength and let you knock him down repeatedly, thus winning the fight.